Certain cyclopropane carboxylic acid derivatives are a useful class of pesticides called "pyrethroids", which have been of considerable interest because of their quick knockdown activity, low persistence as toxic residues and their low mammalian toxicity. Certain derivatives of phenylacetic acids have also been found to have properties of the pyrethroid type. Of particular interest are certain .alpha.-cyanobenzyl phenylacetate pyrethroids. Unfortunately, while such compounds are desirable pesticides, they tend to be difficult or expensive to manufacture due to their relatively complex chemical structures. It is thus desirable to minimize the amount of the pyrethroid that is required to control the pests.